Structure-function relationships in metalloenzymes with multiple redox-active centers

University Of Wisconsin-Milwaukee, Milwaukee WI

Investigators

Abstract

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). The Pacheco-Schmidt research groups are studying three proteins that allow certain bacteria to interconvert ammonia and nitrite. Without these proteins, such an interconversion would be too slow for bacterial survival. The primary aim of the project is to determine how the three proteins, which have broadly similar architectures, are tailored to shepherd the ammonia-nitrite interconversion preferentially in one direction or the other. Indirectly, the research will also supply a deeper understanding of nanoscale electronic device design, since the proteins are essentially conducting devices 5-10 nanometers wide. The proteins will be investigated using a variety of techniques, most notably time resolved X-ray crystallography (TRXRC), a relatively new method that allows one to make movies of molecules undergoing chemical reactions. The technique has enormous untapped potential, some of which will be uncovered during the project. Broader impacts. This project provides research opportunities to high school students and teachers, in addition to undergraduate and graduate students. It will also provide insight into a growing environmental problem: nitrogen cycle imbalance. Ammonia (a major component of fertilizer) and nitrite are two examples of reactive nitrogen; that is, nitrogen usable by many living organisms, as opposed to elemental nitrogen which makes up 89% of the air we breathe, but is directly usable by only a few bacteria. Together, elemental nitrogen and reactive nitrogen constitute the nitrogen cycle. Over the last 50 years the balance between the components of the nitrogen cycle has shifted significantly towards reactive nitrogen species, as more fertilizer was generated to produce food, and more recently biofuels. This shift is having many unintended negative consequences, which will have to be mitigated in the coming years. A better understanding of the processes by which ammonia and nitrite are interconverted may lead to the more efficient use of ammonia fertilizer, and thus help redress the nitrogen cycle imbalance. This award is co-funded by the Molecular and Cellular Biosciences Division and the Inorganic, Bioinorganic, and Organometallic Chemistry program of the Chemistry Division.